1. Field of the Invention
The presently described invention generally relates to anchors and more particularly to so-called drop-in anchors having expandable wedge-forming elements for securement of the anchors within holes in work surfaces of concrete, masonry, brick or comparable materials. The invention specifically relates to anchors that are capable of meeting cracked concrete testing standards.
2. Background
The terms “borehole” or “bore hole” and “hole for the anchor” and “anchor hole” and “drill hole” and/or simply “hole”, as used in this description, are simply convenient terms, as a hole for such an anchor may be formed in ways other than drilling, boring or punching.
The name “drop-in anchor” is a term of art for a general class of anchors that are especially convenient to use. The term is not intended to limit use of the anchor, which anchor is not necessarily “dropped” or otherwise pressed in place; and such anchors may be used in many applications, including overhead insertion in holes drilled upwardly or other than downwardly, and where in any event the anchors can be conveniently pressed in place in a provided hole and there to be initially set awaiting further use, as typically will involve threading into the anchor a threaded male member such as threaded bolt or rod.
Where ease of installation is important, drop-in anchors conveniently allow quick installation. A drop-in anchor allows preliminary setting, that is, initial anchor embedment. Preliminary setting may be carried out by using a setting tool, driven into a central bore of the anchor, to cause initial spreading apart of base portions of the anchor that will cause these anchor portions to come into initial anchoring frictional engagement with the walls of hole that has received the anchor. In the present description, and for convenience herein only, the base is that portion of the anchor that is first inserted into the hole, and thus that portion that is most deeply located in the hole, even though there may be other terminologies (such as “head”) used by some in the art in dealing with corresponding parts of drop-in anchors.
The name “wedge anchors” is a term of art long used to refer to another type of anchor, otherwise known or sometimes known as a sleeve anchor. U.S. Pat. No. 4,720,224 that issued to Peterken on Jan. 19, 1988, is representative of one configuration of a wedge anchor. The assignee of said U.S. Pat. No. 4,720,224 is the same company, operating now under another name, that is the present assignee.
The Peterken U.S. Pat. No. 4,720,224 shows such a sleeve anchor for use in a pre-drilled hole in concrete, masonry and the like. It includes a bolt having a threaded outer end for receiving an internally threaded pressure member. The inner end defines a shank terminating in what is called in the patent a “head” of diameter greater than the shank. The head (which, by analogy, in the present description, and for convenience herein only, can be thought of as that base portion of the sleeve anchor that is most deeply located in the hole), has a tapered wedge-forming shoulder adjoining the shank. A sleeve is disposed concentrically upon the bolt and includes a collar extending along a threaded portion of the bolt at its upper outer end is disposed for receiving longitudinal pressure toward the inner end of the bolt generated by tightening of the nut. An inner portion of the Peterken collar is of petalform configuration, having three petals extending along the shank in closely-spaced side-by-side relationship. The petals are joined at proximal ends to the collar by respective pillars each of narrow arcuate extent, providing windows between the pillars of greater arcuate extent. The pillars have distal ends that contact and ride up the shoulder for radially outward expansion of the sleeve upon tightening of the pressure member. For present purposes, the direction toward the head of Peterken U.S. Pat. No. 4,720,224 could be referred to herein as the baseward direction, as the head portion is inserted into a hole for the anchor, and becomes the base of the anchor.
By comparison a drop-in anchor assembly of a type to which the present invention relates has an internally threaded body, generally of robust wall thickness and an internal bore, part of which is internally threaded. The body may have a radially channeled region. A baseward portion is provided with multiple longitudinal channels extending from a base end forming arcuate sections. The channeled region is annularly recessed for receiving an expansion sleeve. Within the body, inwardly tapered inner walls have diameter reducing toward the base end, that is, that end to be first inserted into a hole of predetermined depth. A setting plug is fitted within the channeled region, and so also is tapered with diameter reducing toward the base. The bore, or through-bore, can receive first an unthreaded setting tool for engaging the plug upper surface for initial setting. The setting plug is initially driven by forcing a setting tool into the bore of the body, so the plug urges portions of the arcuate sections of the radially channeled region axially outwardly for initial setting of the anchor assembly in the borehole. Only then are the internal threads of the bore to receive a threaded male member such as a threaded rod, headless screw, or other screw. The body channeled region can have an annular recess along a portion of the channeled region spaced above the base end with a neck of substantially constant diameter and a tapered portion having tapered outer walls increasing in diameter toward the base end. A clip, or what may be called a sleeve, having petalform distal portions is resiliently fitted on the annular recess in circumferential relation. When a threaded male member is screwed in place and force is placed on the anchor in a direction outwardly of the hole, that is with pull-out force, the distal clip portions ride along the tapered outer walls toward the base end for wedging against the hole wall for final setting of the anchor.
Drop-in anchors and wedge anchors have both been long available. Among the design goals for drop-in anchors are to achieve not only fast and easy installation but, most importantly, to be sure of setting the anchor assembly in the borehole with increased tightness providing enhanced pull-out resistance so as to provide stability and reliability under various conditions.
Among various conditions that may be present are irregularities or surface variations in a hole in which the anchor is to be set. Irregularities may result from dimensional variations or they may vary as a result of the degree to which a hole is cleaned (such as by compressed air or by brushing) after hole drilling.